Tailoring Asymmetric Interface-Triggered Peroxymonosulfate Activation via Staircase-Shaped Edge-Rich-Defective Ti₃C₂T_x by Mechanochemical Treatment: Hydroxyl “Capping” or “Subtraction” Strategy?

Abstract

Modifying the surface functional groups of materials for peroxymonosulfate (PMS) activation for emerging contaminants' degradation has come under the spotlight, and exploring the relationship between terminal functional groups' loss-causing defective sites and the formation of reactive species is still challengeable. In this work, an asymmetric interface derived from the edge-rich defective Ti 3 C 2 T x (ERDT) exposing unsaturated coordinated active titanium atoms was explored by mechanochemical treatment. The stepped cross-section structure improved the degradation rate constant of carbamazepine (CBZ, 0.326 min −1 ) in the ERDT/PMS system, which was 108.9 times higher than that of the bulk Ti 3 C 2 T x (0.003 min −1 ). The results showed that ERDT probably triggered the free radical and nonradical titanium metal oxide species pathways, contributing 51 and 48% to CBZ degradation, respectively. For the metastable Ti−OH in the Ti 3 C 2 T x /PMS system, the Bader charge almost remains unchanged, while the metastable Ti−O−Ti intermediate in the ERDT/PMS system decreases by 0.413 e − to generate the surface-bound oxygen species (Ti(III)−O*−Ti(III)). Namely, ERDT without hydroxyl capping were more prone to produce HSO 4 − ions and Ti(III)− O*−Ti(III) poor-electron region, which easily gained electrons from PMS and CBZ. Along with the edge-defective active sites under mechanical shearing force, a stronger adsorption affinity between PMS and ERDT could be achieved, thus improving the catalytic performance for target emerging contaminants degradation. KEYWORDS: Ti 3 C 2 T x , mechanochemical treatment, peroxymonosulfate activation, edge-rich defects, hydroxyl groups loss

Identification of Superoxide Contribution through the Quenching Method and Model System

“…The production of O 2 •– in chloroform deserves attention. In some studies, − chloroform has been used as a quencher of O 2 •– , which may lead to a contradiction in the contribution of reactive species . Since no inhibition was observed, O 2 •– is often regarded as ineffective; although the conclusion may be a fact due to the low reactivity of O 2 •– , using chloroform as an O 2 •– quencher is unreasonable and may potentially spread misleading information.…”